KR100271083B1 - Infrared camera with thermoelectric temperature stabilization - Google Patents

Abstract

Infrared radiation camera systems have an array of focal planes of microborometa elements in a vacuum package with inexpensive thermoelectric temperature stabilizers. The stabilization temperature can be selected by the designer or user over a wide temperature range, but is mainly used at room temperature. The microboromete is a passive element, and the readout structure contains the sweep of the array with a high level bias current of short duration pulses.

Description

[Name of invention]

Infrared Camera with Thermoelectric Temperature Stabilization

[Field of Invention]

TECHNICAL FIELD The present invention relates to the field of video imaging, and more particularly, to a video camera which generates a visual image from infrared radiation, and more particularly, provides the visual image at a relatively low cost.

[Background of invention]

The present invention is applied to a new type of radiation sensitive focal plane operating near room temperature, i.e., a two-dimensional array of ultra-small borometa (microborometa). The present invention provides an apparatus and method for using the focal plane in an IR image camera without the need for a chopper, 2) an apparatus and method for efficiently retrieving information embedded in the focal plane, and 3) the focal plane Disclosed is a camera system operable to generate a video output signal.

[Overview of invention]

The camera system disclosed in the present invention comprises a reflection or other optical system assembly with an iris for connecting a scene on a focal plane array embedded in a vacuum chamber, and a radiation receiving system preferably comprising a lens. The "window" of the photoreceptive surface or vacuum chamber is not visible at the wavelength of the radiation to be recorded or received by the focal plane array.

The vacuum package includes an array of focal planes added to one side of the thermoelectric temperature stabilizer. The substrate of the thermoelectric temperature stabilizer or focal plane array is a temperature sensing device. The entire assembly is fixed in the base and support structure of the vacuum chamber. The electrical connection consists of several components therein through the walls of the vacuum chamber and permits a bias current to be pulsed to a particular focal plane array element within a certain instant of time to generate an output related to the radiation received therein. Will be. Control induced by the thermoelectric temperature stabilizer passes through the vacuum chamber, and the temperature can be stabilized in accordance with the temperature sensed by the temperature sensor. The high bias source provides a voltage at a constant level that is transmitted through a decoder to a particular focal plane array element to be sensed in the sweep. The output of each device is received by a preamplifier, relayed to a digital signal, and sent to an image processor that generates a video output.

In a preferred embodiment, the window of the vacuum chamber through which the radiation passes is transparent only in infrared light, and the focal plane array composed of microborometa elements is disclosed in United States Patent Application Nos. 06 / 511,369, 06 / 511,370, 07 / 035,118, Similarly to the microborometa focal plane arrays disclosed in 07 / 172,110 and 06 / 887,495, they are properly spaced from the array to dissipate heat.

[Brief Description of Drawings]

1 is a three-dimensional block diagram of the main components of a camera according to a preferred embodiment.

2 is an exploded view of a vacuum package.

3 is a side view of the vacuum package.

4 is an electrical block diagram of a small focal plane array according to one embodiment of the invention.

5 is an electrical diagram of a drive circuit portion coupled with the focal plane array of the preferred embodiment.

6 is a graph of time zone temperature and voltage illustrating the effect of application of pulse bias voltage over time on passive elements of a focal plane array.

Detailed Description of the Preferred Embodiments

[camera]

Referring to FIG. 1, the layout of the camera 100 is shown. Light or radiation received by the lens or reflective optical system 71 is incident through the iris 72 to the surface of the window on the package or vacuum chamber 10 in which the focal plane array (not shown) is embedded. The small dashed line C represents the many pins that electrically connect the rest of the camera with the package 10.

The temperature of the focal plane array is kept constant by the thermoelectric controller 73 which sets the temperature in accordance with the output of the temperature sensor inside the package 10. The temperature at which the array is maintained is also referred to as the stabilization temperature. In the case of using microborometa, this range of stabilization temperatures is tested at zero to 30 ° C., even if higher or lower stabilization temperatures cannot be used.

Line t indicates that temperature information is received by the thermoelectric controller. If the received temperature information is the desired information, no signal is transmitted over the other lines t _a and t _b . However, in a preferred embodiment, the thermoelectric controller can be controlled by transferring power through either line t _a or t _b depending on the direction of the desired temperature change (heater or cooler).

Passive elements of the focal plane array in package 10 need to be polled or send a response command signal by providing a voltage or current. Thus, the array bias is provided by the array bias block 76, which electrical unit is provided with a highly stable (low noise, low drift) voltage supply in a preferred embodiment. We have had some success with simple batteries even though other sources known to those skilled in the art can be used. In a preferred embodiment a voltage is applied to the passive elements of the array in some sequences. Thus, the series of decoders 75 are controlled by the logic controller 77. Logic controller 77 adjusts the current by controlling the decoder of the sweeping sequence (which acts as a large multiplexer) so that each row by the open dress is polled at a time before the poll is opened again in the second sweep. The decoder then steers the bias current provided by the array bias 76 to pin C attached to the package 10.

The output pins C are connected to a series of preamplifiers represented here by block 74. The outputs of these preamplifiers can be output continuously or in buffered form by an analog digital conversion module 78 provided to the respective outputs from each preamplifier a digital display of the analog signal level values input to the preamplifier. Can be. The electrical characteristics of the preamplifier are designed to be stable over time and temperature, and correction for the change is applied to the image processor. The inventors have had some success with the latter technique of using calibration signals injected into the preamplifier. This can also be accomplished by temperature and time independent circuit designs known to those skilled in the art.

The camera is also provided with an image processor 80 in which the operator's console 79 is in electrical control contact. That is, by controlling the method of receiving the digital value already existing in the image processor 80, the operator can change the sensitivity, receive still image information, and variously output the video signal to be output by the image processor 80. Correct or convert. Image processors are well known in the video camera art and typically use digital signal processing circuitry and have various adjustments to the input signal introduced to provide the output video signal illustrated by line 82.

Software control is a preferred embodiment because algorithms that are commonly used are most conveniently executed by software rather than by logic by wiring. This software control enables different algorithms to be executed in different instants of time, and signals from different ranges of arrays can be processed with different processing algorithms, making it possible to execute even those that are difficult to execute in hardware.

This camera design has some advantages that are not revealed.

The iris can be instantaneously closed so that it can average several image frames and record the digital data in a long-life digital memory that may be in the image processing system (i.e. after camera manufacture, i.e. during camera operation). If desired, it can be used as an alternative to simple means of lens caps or shutters. In normal camera operation, the iris 72 is partially closed if it is desired to remain permanently open or to reduce the drop in radiation intensity on the focal plane. The image processor subtracts a signal from the digital data of the long lifetime memory on a pixel-by-pixel basis. This provides offset correction for each pixel of the image seen by the viewer, and such conditions and processing are known to those skilled in the art. The focal plane is maintained at a stable temperature by the TE stabilizer, the electrical characteristics of the preamplifier are unchanged, no change can constitute electrical polling of the array, and no chopper is required to disturb the radiation from the scene. . The absence of a chopper results in a number of good advantages: cheaper and more reliable cameras, lower electron speed conditions and the removal of low sensitivity resulting from the chopper's periodic radiation disturbances.

[Package for Array]

Referring to FIG. 2, the vacuum chamber 10 is shown in an exploded view. The package consists of a base plate 11 comprising openings 12, 13, 14 and 15 for connection to a camera and a peripheral wall structure 16 having an inner step 17 on which pads 18 are positioned. . Only a few of the wires 19 shown are connected to these pads. Basically, this exploded view and its limited elements are not intended for a limited purpose, but are shown for illustrative purposes only.

The wall 16 has an opening 53 in the upper surface of the base plate 11 and surrounds the boundary area 54 in the interior of the wall. The opening 53 extends into the tube 50 with the interior space represented by the dashed line and finally with the product of the preferred embodiment pressed at 51. Getter 55 may also be used. The thermoelectric temperature stabilizer 20 is assembled in the space of the boundary region 54 of the finally completed package. The thermoelectric temperature stabilizer consists of a top plate 20a and a bottom plate 20b, usually of beryllium oxide, incorporating a layer of other material such as bismuth and / or antimony or other suitable materials known in the art. Power lines "-" and "+" apply power to one of the top and bottom plates, thereby cooling or heating the device. Surfaces such as top surface 26 are preferably metalized by soldering to the top surface 26 of the substrate 11 on one or the bottom surface of the focal plane array. For simplicity of thermistor, the temperature sensing device 27 of the preferred embodiment is attached to the top surface of the thermoelectric temperature stabilizer 20. Many temperature sensors are currently in development or widely available and can be used depending on economic aspects. If the temperature sensor is small enough, the temperature sensor may be located on its focal plane array chip. This will meet the designer's needs. So all that is required is that a very accurate reading of the temperature of the focal plane array can be provided by the temperature sensor.

The inventors also have some success using temperature sensors fabricated on focal plane array chips. These sensors are periodically polled by the focal plane information reading electronics in the same manner as the microborometa, and the temperature data is transmitted to the image processor in the same manner as the microborometa signal. The present inventors have had some success using image processors to utilize these temperature signals to improve image quality by correcting for small temperature variations in the camera. These can be microborometa that are configured to be insensitive to infrared radiation.

The focal plane array chip 30 preferably has a coupling head, ie, a lead 31, around its edge. The focal plane array element, which is sensitive to radiation, is disposed in the region 33 of the chip of the preferred embodiment. If a temperature sensor is used on the focal plane array, the temperature sensor is most preferably included in the area 33.

The top away from the package is a transparent window 40 in the form of radiation which is expected to be received by the focal plane array 33. Edges around the bottom of this window are metallized in the preferred embodiment by soldering. The focal plane array device of the presently preferred embodiment is a passive micro-coated with vanadium oxide which provides a change in resistivity based on the amount of infrared radiation received by each device in a manner related to that disclosed in US patent application Ser. No. 07 / 035,118. Borrometa device. In a preferred embodiment of this infrared sensing an antireflective germanium window is used for the window 40. In the package of the presently preferred embodiment, the base 11 and its peripheral wall 16 are made of custom-made IC manufactured by Kyocera, Japan, made of aluminum oxide (Al ₂ O ₃ ) for the base plate and wall of copper alloy. Package. The tube of the preferred embodiment is copper, and the getter is a metal alloy known to those skilled in the art operating away from the apparatus after the tube is used to pump air into the sealed package 10. The getter is pushed up to seal towards the package of the tube 50 and the package is sealed by pressing the tube at 51. In the preferred embodiment all parts are soldered, but the electrical connections are joined. However, improvements in the technology and practice of attaching electrical leads and components together can be implemented in different ways within the scope of the present invention. Similarly, materials which can be clearly substituted for the above can be replaced without exceeding the scope of the present invention.

Referring to FIG. 3, a side view of a package 10 having a getter 55 therein and having a copper tube 50 coupled to the base plate 11 is shown. Wires W, Wt, Wt _b and Wt _a provide power and readout information to three devices in vacuum space 53. From these wires the leads or pads of step 17 are coupled to wires 19 through walls 16, which are preamplifiers of block 74 in FIG. 1 and thermoelectrics in block 73 in FIG. It may be coupled to a connector to an external device such as a controller and a decoder that supplies a bias voltage through block 75 of FIG. The radiation reaching the window 40 at the right wavelength R1 travels through the window. Radiation other than the perpendicular wavelength R2 is reflected at or absorbed by the window 40. As described above, several surfaces are held together in a preferred embodiment by soldering the soldered connections 61, 62, 63, 64. As described above, these connections can be made by other means, but soldering is preferable at present.

With reference to thermoelectric temperature stabilizer 20 these devices are currently in use from several manufacturers, and the preferred source is Marlow Industries, Dallas, Texas. The infrared sensing focal plane array has 80,000 elements, and the preferred thermoelectric cooler is Marlow Industries model number SP5030-03-BC.

[Read Information from Passive Device]

Referring to FIG. 4, there is shown a schematic diagram of focal plane array 33A having a number of inputs (four here can be represented by m) and a number of outputs (here but three can be represented by n). . A bias through which an entire row of pixels, such as pixel P at address (2, 3) or (2, n), will be driven to provide an output indicating its status on output line (1, n) through the input line. Current is simultaneously supplied to each input line. In this figure, each pixel, called an element, unit, microborometa or borometa, receives a pulsed current from input line (1, m) through diode (d), denoted d (m, 1) in the figure.

The preferred implementation is the bipolar transistor of FIG. 4 because it requires smaller currents shown in rows. Circuit operation is the same for diodes and transistors. In addition, a field effect transistor having a very small change can be used. Conceptually, any type of switch can be considered as a diode.

The operation principle will be described with reference to FIG. In the case of passive pixels, the electrical properties are changed by changing the temperature due to the reception of radiation or the reception of radiation, and a graph of temperature and voltage versus time is shown for illustrative purposes. In the most preferred embodiment, of course, the pixels or microborometa and the window are transparent to infrared radiation. The microborometa changes in temperature due to the reception of radiation through the window and the amount of deflection through the microborometa surface structure, and the resistance decreases as the heat of the microborometa assembly increases. Vanadium oxide material is reduced in resistance due to temperature rise. There are other materials (ie metals) that change in opposition to the resistance.

The voltage level, represented by line 5 in FIG. 6, is to supply pulse bias current over time to a single microborometa of the focal plane array. The pulse width in an 80,000 pixel array is approximately 5-6 dB based on the 14 addressing pixels of the preferred addressing structure at a time. Temperature curve 6 shows that a single microborometha meta temperature can rise about 2 ° C. for each time of a current pulse of approximately 200-300 microamps. The 22 ° C line represents the desired temperature for the focal plane array. Note that the temperature of an individual pixel flows above 22 ° Celsius at all times when not pulsed with current. It can be appreciated that the excess temperature change is caused by the bias current pulses illustrated in FIG. 6 and results in additional temperature change with radiation induced from the scene.

22 ° C. is expected to be the stabilization temperature for the focal plane array of the preferred embodiment. At this temperature, a temperature change of about ten degrees in the microborometa may provide a noticeable change in resistance, ie about 0.2%.

The high bandwidth amplifier is used in the preamplifier 74 of FIG. 1 due to the short span of time for reading signals in the array to provide a moving video image that can be perceived by a human in real time. The large current compensates for the inherent noise of these high bandwidth amplifiers. The large bias current, which can be safely used as a pulse bias, proportionally improves the sensitivity of the microborometa, which is easy to compensate for the inherent noise of a high bandwidth amplifier, and enables IR imaging with a borometa array.

The pulse bias current structure is used to read the information of the aforementioned passive device such as US Pat. No. 3,900,716 for the memory chip. Nevertheless, this conventional structure is not applied to focal plane array technology. Even in the early stages, it is not authorized to run here.

Note that in the present invention, since the bias current is applied to the short pulse, a high bias current that damages the pixel may be used if the pulse is applied continuously. The sensitivity of the microborometer is higher than the pulse bias current because its sensitivity is improved approximately in proportion to the bias current level.

FIG. 5 shows a detailed electrical wiring diagram of the focal plane array portion of the passive pixel. The passive pixel illustrated here is one level RP connected between column 91 and row 95 by transistor QP.

The borometa RP and pixel transistor QP are located at the intersection of each row and column (each of the borometa and pixel transistors are located at the row / column intersection, but only one of these configurations is shown here). Each row is controlled by transistor QR (1-4) and resistor RR (1-4). Each column is controlled by transistors QC1 (1-4) and transistors QC2 (1-4). Rows are grouped into a row group consisting of several rows in each row group (only two are shown here). The columns are grouped into a row group consisting of several columns of each column group (only two are shown here). This clustered configuration allows for a large array to be controlled by several control lines (row group selection, row selection, column group selection). Several signal lines (shown only S1 and S2) carrying signals to several preamplifier transistors and resistors (here only QAMP1, AQMP2, RC1, RC2 are shown) provide the amplified output signals (0UT1, OUT2).

In operation, one row is biased to the "ON" potential by application of a control signal to the row select and row group select control lines, and all other rows are biased to the "OFF" potential by the RR resistor. At the same time, a control signal is applied to the column group selection line to read the signal from several (only two) microborometa RPs at the same time as the row selection. The information reading signal consists of a current flowing into the columns of the selected column group. The information read signal current is converted into a voltage signal amplified by a preamplifier transistor (only two are shown). The control signal is applied to the column group select line until all microborometers of the selected row have been read. Then another row to be biased to the "ON" potential is selected and the process is repeated. This operation continues until all microborometa of the desired rows and columns have been read.

In such an operation mode, the bias current flowing through the borometer is in the form of a short pulse, and the temperature of the borometer changes in a pulsed manner. This pulse bias operation allows a higher bias current to be applied than is allowed with a continuous bias current (continuous bias current is kept smaller to prevent destruction of the pixel or borometer by overheating), and to infrared radiation Correspondingly providing higher sensitivity.

It is possible for the current pulse interval to be selected so that simultaneous readout of individual pixels is at an acceptable value for optimal array operation.

Grouping rows and columns into row and column groups makes it possible to control a large array with a relatively few control lines.

VSUB is a bias potential applied to the circuit of FIG. The purpose is to hold the transistor biased for inherent operation and provide a "sink" for pulse bias current. The name arises from the fact that this connection occurs on the silicon chip substrate. VROW is applied to resistor RR to enable these resistors to bias unused rows " OFF ".

Claims (23)

An optical assembly that provides light / infrared radiation to the focal plane array 33 of infrared sensing microborometries on a semiconductor substrate 30 that is kept constant at a selectable temperature over a wide area by the thermoelectric temperature stabilizer 20. (71), wherein the thermoelectric temperature stabilizer is controlled by a controller (73) that maintains temperature in accordance with a signal received from a temperature sensor (27) of a thermal bond adjacent to the array. 4. The output of claim 1 wherein the focal plane array provides an output signal by a decoder 75 that selects a particular column and row address of the array by providing a bias current from the bias current source 76 to the array at short interval pulses. And the selection of the column and row addresses is determined by a logic controller (77) which generates a signal for setting a switch of the decoder in a pattern designed to sweep the entire array at an appropriate ratio. 3. The infrared camera of claim 2, wherein the level of bias current at which a pulse is generated in each pixel is greater than the safe level for each pixel if the pulse is present for a long duration. 3. An infrared camera according to claim 2, having a serial output of analog signal values returned from said sweep of said focal plane array. 3. The serial output according to claim 2, wherein the serial output is provided after reception of separate analog outputs from the row and column serial sweeps by separate preamplifiers for each pixel address, and the output of the preamplifier 74 is the respective analog output. An infrared signal received by an analog / digital module 78 for converting a value into a digital representation of the analog value and transmitting the converted value to an image processor for converting the received value into a standard video output signal. camera. The infrared camera of claim 1, wherein the stabilization temperature is close to room temperature. The infrared camera of claim 1, wherein the camera does not have a chopper. The infrared camera of claim 1, wherein the thermoelectric temperature stabilizer maintains a constant focal plane array temperature at which a chopper is not required. A device for holding a semiconductor device in a vacuum at a relatively constant temperature, comprising: a substrate having first and second surfaces, the substrate having an opening surrounded by a continuous wall structure along a portion of the first surface, and through the opening; A thermoelectric temperature stabilizer mounted securely to a surface region bounded inward by the wall sphere and mounted on the opposite surface to allow fluid to pass therethrough, and mounted to the semiconductor device in thermal proximity to the sensor array The thermoelectric temperature stabilizer and the semiconductor device sealed with a temperature sensor and a semiconductor device in the internal space formed by the temperature sensor, the first surface, the window for receiving some radiation and the wall structure. A window for holding a semiconductor device, comprising a window for receiving the . An apparatus for maintaining a sensor array in a vacuum at a relatively constant temperature, comprising: a substrate having first and second surfaces, the substrate having an opening surrounded by a continuous wall structure along a portion of the first surface, and through the opening; A thermoelectric temperature stabilizer mounted securely to a surface region bounded inward by the wall structure and mounted on the opposite surface to allow fluid to pass therethrough, and mounted to the sensor array in thermal proximity to the sensor array And a plurality of radiations, the thermoelectric temperature stabilizer and the sensor array sealed with a temperature sensor and a sensor array in the interior of the space formed by the temperature sensor, the first surface, the window containing some radiation and the wall structure. To maintain the sensor array, characterized by having a window for receiving the Device. An apparatus for holding an infrared sensitive semiconductor device in a vacuum at a relatively constant temperature, comprising: a substrate having first and second surfaces, the substrate having an opening surrounded by a continuous wall structure along a portion of the first surface, and the opening; A substrate formed with an opening enclosed by the wall structure to allow fluid to pass therethrough, and a surface region firmly mounted to the surface region bounded inward by the wall structure to allow fluid to pass through the opening, A thermoelectric temperature stabilizer mounted with an infrared sensitive semiconductor device, a temperature sensor mounted to the infrared sensitive semiconductor device in thermal proximity to the sensor array, the first surface, a window for receiving some radiation, and a wall structure. The thermoelectric temperature stabilizer, the temperature sensor and the internal space formed by And a window for receiving some radiation, said infrared sensitive semiconductor device being hermetically mounted with an infrared sensitive semiconductor device. 10. The device of claim 9, wherein a sealable tube member is mounted to the second surface around the opening. 13. The apparatus of claim 12, wherein a getter is disposed in the tube prior to sealing. The apparatus of claim 10, wherein a sealable tube member is mounted to the second surface around the opening. 15. The apparatus of claim 14, wherein a getter is placed in the tube prior to sealing. 12. The apparatus of claim 11, wherein a sealable tube member is mounted to the second surface around the opening. 17. The apparatus of claim 16, wherein a getter is placed in the tube prior to sealing. 13. The device of claim 12, wherein a sealable tube member is mounted to the second surface around the opening. 19. The apparatus of claim 18, wherein a getter is disposed in the tube prior to sealing. A method of reading a change in resistivity of a passive radiation receiving unit of n vs m, the method comprising: exposing a radiation receiving surface to a predetermined irradiation surface to be observed and changing the resistivity of the receiving unit in relation to the radiation dose received from the irradiation surface And sweeping the accommodating unit with a short duration pulse of very large bias current so that the unit remains stable if the pulse is long and the pulse is long. And wherein each said unit has a time to return to a stabilization temperature prior to generating a short duration second bias pulse in each said unit. 21. The method of claim 20, responsive to temperature changes induced only by infrared radiation. 21. The method of claim 20, responsive to temperature changes induced only by infrared radiation. 21. The method of claim 20, wherein the temperature change affects a change in resistivity of the radiation receiving surface.